2010/3/7 Russell King - ARM Linux <linux@arm.linux.org.uk>:> On Sat, Mar 06, 2010 at 02:07:12PM +0100, Thomas Koeller wrote:>> Am Donnerstag, 4. März 2010 22:36:34 schrieb Russell King - ARM Linux:>> > Cache maintainence is done using virtual addresses for L1, and>> > physical addresses for L2. There's the need for virtual addresses>> > to be translatable to physical addresses, which is only true for>> > the kernel direct mapped region (pages between PAGE_OFFSET and>> > high_memory).>>>> Isn't the mapping created by vmap() sufficient for the virt/phys>> translation? In which way is this case different from a buffer>> passed in from user space, where the constituent pages are not>> in the directly mapped kernel region either?>> No different.>> The requirement is that dma_map_single() is passed a virtual address> in the kernel direct-mapped memory region, which is translatable using> virt_to_phys() and friends.I had encounter a similiar problem and I simply allocated a newbuffer, copy the data, then DMA. It seems slow and stupid.

I'm wondering wether could I translate the vmap virt to phys(don'tknow how to yet), then use phys_to_virt to get the virt indirect-mapped memory region?

Is there other possible ways?

> Anything which requires a page table lookup to obtain the physical> address is just not acceptable - that requires taking locks and other> messy things, plus is grossly inefficient.